BDT Radio 1b CMV 2009/09/04 Basic Detection Techniques 1b (2011/09/22): Single dish systems Theory: basic properties, sky noise, system noise, Aeff/Tsys, receiver systems, mixing, filtering, A/D conversion Case study: LOFAR Low Band Antenna BDT Radio 1b CMV 2009/09/04 Basic Detection Techniques Visit to Dwingeloo for APERTIF measurements 2011/09/29 13:00-15:00 NS to Beilen: 13:31-13:58 NS fm Beilen: 16:59-17:28 Transport Beilen Dwl vv will be arranged by ASTRON Call (Diana van Dijk) in case of problems Host is Laurens Bakker APERTIF System Engineer) BDT Radio 1b CMV 2009/09/04 Sensitivity Key question: Whats the weakest source we can observe Key issues: Define brightness of the source Define measurement process Define limiting factors in that process BDT Radio 1b CMV 2009/09/04 Brightness function Surface brightness: Power received /area /solid angle /bandwidth Unit: W m -2 Hz -1 rad -2 Received power: Power per unit bandwidth: Power spectrum: w(v) Total power: Integral over visible sky and band Visible sky: limited by aperture Band: limited by receiver BDT Radio 1b CMV 2009/09/04 Point sources, extended sources Point source: size < resolution of telescope Extended source: size > resolution of telescope Continuous emission: size > field of view Flux density: Unit: 1 Jansky (Jy) = W m -2 Hz -1 BDT Radio 1b CMV 2009/09/04 Reception pattern of an antenna Beam solid angle ( A = A/A 0 ) Measure of Field of View Antenna theory: A 0 a = 2 BDT Radio 1b CMV 2009/09/04 Black-body radiation General: Plancks radiation law Radio frequencies (hv